The most striking renal feature in autosomal dominant polycystic kidney disease (ADPKD) is the presence of hundreds of fluid-filled renal cysts, which grow over time and slowly destroy kidney structure and function. However, even when therapeutic reduction of cyst growth is achieved, fibrotic processes remain unchecked and continue to influence disease progression. The research objective of this application is to identify and manipulate renal fibrotic mechanisms to delineate their roles in the pathogenesis of cystic kidney disease. In Aim 1, we will utilize a combination of cell-type specific shRNA vectors and a new hydrodynamic pressure method for delivery of genetic material to kidneys in order to test our hypothesis that anti-fibrotic relaxin- mediated signaling within fibroblasts or renal epithelial cells (in vivo) will inhibit TGF?R2 signaling, resulting in reversal of pro-fibrotic gen expression profiles and cellular responses associated with renal fibrosis in cystic kidney disease. In Aim 2, we will delineate the primary biochemical pathways impacted by relaxin-mediated abrogation of TGF-?/Smad signaling in human cystic renal epithelial cells and fibroblasts, under in vitro conditions designed to test cell-cell and cell-matrix interactions. Thi proposal outlines a five-year training plan at the University of New Mexico under a team of mentors and consultants with expertise in the fields of nephrology, biochemistry, matrix biology, renal physiology, tissue engineering, chronic instrumentation, and clinical-translational research. The proposed research design will provide Dr. Ward with training in intravital imaging, in vivo delivery of genetic material, and development and utilization of advanced three-dimensional bio-artificial matrix scaffolds. The goal of this mentored K01 award is to provide the candidate with the specified training and environmental excellence necessary for Dr. Ward to transition to a successful independent investigator. The candidate will use the studies outlined in this proposal to develop an independent line of research devoted to identifying molecular mechanisms of renal fibrosis, defining how these mechanisms drive chronic kidney pathogenesis, and developing specific mechanism-based therapies for fibro- proliferative kidney diseases. In addition to the above aims, Dr. Ward will 1) develop a comprehensive understanding of matrix biology, mechanisms of fibrosis, intercellular signaling, and chronic kidney disease through mentoring, extramural workshops, and topic specific national conferences, 2) receive formal training in biostatistics, biomedical ethics, clinical-translational study design, and animal model development though coursework and mentoring, and 3) participate in professional development workshops and courses focused on grant writing and review, best mentoring practices, laboratory management and leadership, and scientific communication. The relevance of the proposed studies to clinical ADPKD is substantial as the candidate's research will identify specific mediators of renal fibrosis and inform on the development of new therapeutics to inhibit fibrotic progression in cystic kidney diseases.